Williams duo Felipe Massa and Valtteri Bottas both struggled on Friday in practice for the Singapore Grand Prix.

Bottas was sixth in the opening session, but slipped back to a lowly 17th in FP2, and complained that they just couldn't get the supersoft tyres to work around the tight and twisty Marina Bay Circuit, all seemingly very reminiscent to Monaco and Hungary.

"With the primes, it didn't seem too bad, more or less what could be expected, so we could be just about in the top ten on a Friday," Bottas explained.

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"But then we went to the option and we couldn't get the same lap time gain that the others [could]... we just couldn't get the tyres to work.

"I had a little bit of traffic on the out-lap [too], which compromised me a bit, but I think it shows we are really sensitive with the tyre temperatures."

"I could see the surface of the tyres were new half way around the timed lap, so I knew it wasn't really working," he added.

"We need to analyse it. It isn't the first time is has happened and we need to find the reason.

"We need to be in Q3 - and then when we get to Q3 it is normally close, so hopefully closer to top five."

Meanwhile, in contrast, team-mate Massa went from P17 in FP1 to 11th in FP2, but also stressed that they need to "understand" the tyres better.

"I think it was a day to understand about the tyres and the degradation... it was OK, the first feeling," he continued.

"Maybe I improved from FP1 to FP2, understand the tyres better, but now we need to analyse long runs to see where we are from the others.

"It's true that it is a track that is really good for others teams like Red Bull and Ferrari, they can even be closer to Mercedes here. It is a race that we need to try to do everything we can to score points.

"Maybe we cannot be as competitive as others, but you never know, in this race many things can happen."

Pressed on where Williams are compared to its rivals, Massa added: "It is too early to say. We need to wait until qualifying to be 100 per cent sure. Qualifying will be very important, because it is the track where overtaking is difficult."